Wavelength

From Slackerpedia Galactica

The length of a wave.

Duh.

More thoroughly, the characteristic length of wave, applicable to both acoustic and gravity waves in physical media, and to electromagnetic waves (i.e. photons). Because all photons travel at the same speed in a vacuum, the thing that makes one photon have a different energy than another is its wavelength; the shorter the wavelength, the greater the energy, and vice versa. The two are related by the equation E = hc/λ, where λ (the Greek letter lambda) stands for the wavelength.